turbotuner20v

I'm trying to find anyone who has broken a stock crankshaft. Seems like even online where the ratio of complaints to complements is usually 99:1, nobody complains about broken oem cranks.


If you've broken one, what was your setup and thoughts about the failure?



I'm running a Gen IV 6L iron block, stock crank, eagle rods and wiseco pistons with arp mains and head studs with lsa heads and ls9 gaskets. Right now I'm running an f1a @ ~20psi making 930whp (which is all I built the motor expecting) but I'm getting the itch for an f1x and am curious if that will expose the crank as the weak link. Thinking ~1050whp or so with whatever extra load that puts on the crank snout.

RonA

iTrader: (1)

I was curious about this as well, but was told to upgrade the crankshaft by the dealer selling the prochargers. I bit the bullet and ordered a Callies crank on Friday. On the plus side, they are really nice people to deal with.

coolmanvette75

iTrader: (2)

I know Flash broke a stock one in his old motor...

HexenLord

Supercharger setups are going to be putting a lot more stress on the crank than other setups. That being said, most of the people breaking stock cranks were spinning them pretty high. Don't forget to post RPM when talking about breaking parts.

Chris'stransam

iTrader: (7)

I have been told that the stock crank is good for 1000hp , and what's normally breaks them is the mains start to give and the crankshaft walks then it breaks . I am using a stock for my build .

Camaro9969

iTrader: (12)

I will find out myself. Weisco pistons compstar rods arp mains we will see if it can handle 1200hp

The Alchemist

iTrader: (19)

I think the notion that the superchargers are harder on cranks is a little inaccurate. Sure, if you have a static tensioner that you have to crank down to a severe level, then sure, it puts more stress on the snout of the crank, but for those of us who run a spring loaded tensioner, I don't think it adds that much more stress than the 2 belts that are already on the snout.

I tend to believe that at equal hp levels, a turbo will stress the mains more than a supercharger since the rate of increase in torque is much higher in a turbo application than a supercharger application. For my 760hp setup, I made 700ft/lbs of torque, that came in smoothly, which isn't nearly as harsh on the mains as a turbo that snaps into a boost curve.

Also, another thing to consider is what's done to the bottom end to help. I have ARP studs in my mains, which helps, but other people pin their mains as well to help with distortion. All those things help to increase the longevity of the bottom end, how much, I don't know.

turbotuner20v

Any details on how long it lasted, power, 2step impact, how it broke? That's the first confirmed case I've heard of.

Exidous

iTrader: (11)

Torsionally, I would think the stock crank would let go near the rear main. I have seen pictures of twisted cranks before but I must admit that more of them were aftermarkets than stockers. This is probably due to most of the really high power guys are all running aftermarket by default due to stroke.

If you do everything right, bearing clearance, pinning, balance and strong main studs and or billet mains it would go a long way to make it last.

I would also think a high power stick what just grabs would be much worse than an auto on a transbrake being that the motor is already loaded.

forcd ind

iTrader: (7)

running a transplant cog kit on mine, D1SC with 14 lbs
I do worry about it, as the end of the crank pulley is pretty far from the end of the crank-I don't run the belt real tight-its been on a year, no track time but several (well, maybe more) 6500 shifts, lol

smokeshow

iTrader: (17)

I had a set of ball bearing twins, and it definitely didn't 'snap' into boost. It was quick...but no snap. When people talk about blowers breaking cranks, its positive displacement or twin screw stuff. That is the only forced induction that will 'snap' into boost.

That said....I have sheared off a crank pin with a D1SC before. They get into boost more gradually, but they can still put a hurting on stuff.

Zero_2_Sixty

I am guessing the flex of the crankshaft is what breaks them. When they break its generally not at the snout.

RonA

iTrader: (1)

I think the factory underrates most engines. The LS engines are rated at 300ish hp, but hold up to around 1000 if you keep the torque down. Same with the diesels, they are rated around 300hp and 600ish torque and will hold 1000ish if you keep the torque down. Bad tuning probably ruins more engines than high hp.

ddnspider

iTrader: (26)

If you compare a properly setup street turbo car, torque can rise at a very fast rate compared with the linearity of a centrifugal setup. My torque curve is fairly severe, not on the level of a twin screw, but compared to a centrifugal, it's a much steeper slope. I think that's what alchemist is getting at.

Old Geezer

iTrader: (3)

And, on a belt system, heavy reverse torsionals take place when you lift....

turbotuner20v

So far Bryan's motor is the only one that broke a stock crank?

turbotuner20v

Any details on his setup? Arp mains, iron block?

How'd he catch it?

MustangLS

iTrader: (5)

Carlos (98cobrakiller) was more than likely putting down close to 1000RWHP at 23psi, which is easily in the 1150-1200 hp level at the flywheel. I don't recall what RPM he was shifting at.

Exidous

iTrader: (11)

The cog setup's help a lot to reduce stress on the snout and they don't have to anywhere near as tight as the serpentine setups.

As far as stress when you lift off:

http://www.atiracing.com/superpulley/

ittwgn

I havn't seen it before but I broke a main cap